The present invention relates to a numerical control for machine tools, robots, or the like that are controllable using a machining program with tool-related machining operations and position elements.
In manufacturing individual parts and small series of workpieces using numerically controlled machine tools or robots, the programming sequence of a numerical control represents an important cost factor, since programming is performed by workshop-oriented programming predominantly on the machine tool, especially in small manufacturing shops. In this process, programming times and machine shutdown times add up to a considerable portion of the unit cost of the workpieces that are manufactured.
One considerable disadvantage of numerical controls and the respective programming languages used today is the block structure requirement according to DIN 66025, which assumes basic knowledge of the significance of G and M functions, but also requires mastery of the respective control dialect. Thus, the purchase of a numerically controlled machine tool or new generation robot involves not only costly training of an employee, but also training of a new specialist each time, whose function can only be assumed by other employees either only partially or not at all in his or her absence, since traditionally the control of a machining sequence is determined by the programmer at the time the program is written.
This traditional programming method is elucidated in the following with reference to an example.
FIG. 1 shows a workpiece W, to which different internal threads are to be applied. The machining steps will be hereinafter referred to as machining operations or machining objects; the positions will be referred to as position elements. Accordingly, the above-mentioned internal threads on position elements will be referred to as GO1 through GO4 and GO5 through GO8, each of which describes a row of holes with four holes aligned along a straight line.
A complete sequence of machining operations and positions describes a machining task. A sequence is completed if at least one position element follows at least one machining operation.
In order to make an internal thread using a machine tool according to FIG. 1, in principle the following machining steps must be executed:
1. Center with a centering bit
at the positions of row of holes 1
at the positions of row of holes 2
2. Bore with core bit
at the positions of row of holes 1
at the positions of row of holes 2
3. Cut thread with a thread cutter
at the positions of row of holes 1
at the positions of row of holes 2
Machining steps 1, 2, and 3 are therefore individual machining operations performed on the position elements.
Traditionally such tool-related machining is performed by writing a CNC program. In a CNC program, the machining operations are recalled in the form of modal cycles; then the position elements are defined in the form of positions (see previous example). Since the cycles are modal cycles, they are executed by the machine tool in each consecutive position as the machining program is run. A CNC machining program can be produced by the worker directly generating the program on the machine or via a post-processor run from a CAD/CAM program. The sequence control is therefore determined at the time the program is produced by the programmer or the CAD/CAM system.
Therefore, sequence control and thus the duration of the machining process is heavily dependent on the skill and experience of the programmer on the machine. Depending on the optimization of the machining operation concerning the machining program, this may also involve multiple changes of each tool.
An object of the present invention is therefore to control the sequence of a machining task so that the given operations are performed on all position elements so that each tool is only changed once. In this manner, it is always ensured that the time per unit is optimized regardless of the skill of the programmer and therefore productivity is improved.
To achieve this object, the numerical programming according to the present invention provides that the numerical programming includes a sequence control by the use of cycles, according to which machining operations and position elements for each machining task can be performed in the machining program, depending on their technology-dependent sequence in the machining program, so that each cycle for an operation can be selected as a modal cycle, with all cycles for a position element being selected consecutively for a machining object and the respective operation being performed at the position of the respective position element before the following cycle is selected as a modal cycle for an operation.
In a first advantageous embodiment of the numerical control according to the present invention, a particularly effective implementation of the aforementioned sequence control is achieved in that a machining buffer is provided, in which the data of the respective machining object and position element can be written for each machining operation. This can be done, in particular, at the time when the machining program is running.
In another advantageous embodiment of the numerical control according to the present invention, the sequence control according to the present invention can be executed at the time of the program execution. This is done by the sequence control operating in real time mode at the time of the machining program execution. This can be done by interpreting the machining buffer and control according to the above-described sequence.
Another advantageous embodiment also facilitates the description of geometric structures in that position elements can also describe, in particular, position series, position grids, or position circles or obstacles.
In another advantageous embodiment of the numerical control according to the present invention, tool axis path optimization is also possible. This is achieved by the fact that return motions onto a global return plane during the cycle can be avoided by the sequence control for the position elements located at different levels in that return positioning is only performed up to a local safety level of the position element located at a higher level.
In another advantageous embodiment of the numerical control according to the present invention, a more effective implementation of the machining programs is also made possible. This is achieved by the fact that position elements can be used multiple times for different machining operations.